Enhanced decolorization of azo dye in a small pilot-scale anaerobic baffled reactor coupled with biocatalyzed electrolysis system (ABR-BES): A design suitable for scaling-up

A four-compartment anaerobic baffled reactor (ABR) incorporated with membrane-less biocatalyzed electrolysis system (BES) was tested for the treatment of azo dye (alizarin yellow R, AYR) wastewater (AYR, 200mgL^-1; glucose, 1000mgL^-1). The ABR-BES was operated without and with external power supply to examine AYR reduction process and reductive intermediates with different external voltages (0.3, 0.5 and 0.7V) and hydraulic retention times (HRT: 8, 6 and 4h). The decolorization efficiency in the ABR-BES (8h HRT, 0.5V) was higher than that in ABR-BES without electrolysis, i.e. 95.1±1.5% versus 86.9±6.3%. Incorporation of BES with ABR accelerated the consumption of VFAs (mainly acetate) and attenuated biogas (methane) production. Higher power supply (0.7V) enhanced AYR decolorization efficiency (96.4±1.8%), VFAs removal, and current density (24.1Am^-3 TCV). Shorter HRT increased volumetric AYR decolorization rates, but decreased AYR decolorization efficiency.